Polysiloxane polyols are well known in the art. Japanese Patent Publication 48-19941 describes polysiloxane polyols which are obtained by the dehydrogenation reaction between a polysiloxane hydride and an aliphatic polyhydric alcohol or polyoxyalkylene alcohol to introduce the alcoholic hydroxy groups onto the polysiloxane backbone. In practice, however, it is difficult to obtain an industrially significant yield of such polysiloxane polyols because such a hydrosilylation reaction readily gels. Another problem encountered with this hydrosilylation reaction is the difficulty in obtaining a solvent capable of dissolving both reactants. Strongly hydrophilic alcohols such as polyglycerols are highly soluble in alcohols and water, but insoluble in hydrocarbon solvents. Polysiloxanes, however, are generally only soluble in hydrocarbon solvents such as toluene or n-hexane.
U.S. Pat. No. 4,431,789 to Okazaki et al. discloses a polysiloxane polyol which is obtained by the hydrosilylation reaction between a polysiloxane containing silicon hydride and a polyglycerol compound having an aliphatically unsaturated linkage in the molecule. Examples of such polyglycerol compounds are those obtained by the reaction of allyl alcohol and glycidol or by the reaction of diglycerin and allyl glycidyl ether. This reaction, a so-called hydrosilylation reaction, is the addition reaction between an organosilicon compound having a hydrogen atom directly bonded to the silicon atom, i.e., a polysiloxane hydride, and an organic compound having aliphatic unsaturation in the molecule carried out in the presence of a catalytic amount of a Group VIII noble metal. The hydrosilylation reaction can proceed readily in the presence of an alcoholic solvent which can dissolve both reactants. The resulting polysiloxane polyols are useful as non-ionic surface active agents. However, the polysiloxane polyols have limited compatibility with organic resins and solvents which restricts their use in solvent-borne coatings.
U.S. Pat. No. 5,260,469 discloses butoxylated polysiloxane polyols which arc disclosed as being useful in cosmetics. U.S. Pat. No. 5,248,789 discloses epoxy functional polysiloxanes which are formed by reacting a polysiloxane-containing silicon hydride with allyl glycidyl ether.
The prior art references do not teach further reacting the hydroxyl groups of the polysiloxane polyols with other groups to provide various reactive functional groups pendant from the polysiloxane backbone. Such reactive functional groups allow incorporation of the polysiloxane moiety into curable compositions which can contain a variety of reactive components, including a variety of curing agents. There is no indication in the references of using either the polysiloxane polyols or their derivatives as major components in curable compositions.